This invention relates to a method and apparatus for cooling a brake drum. Specifically, an impeller is mounted to a brake drum and a non-rotating stator is mounted in an overlapping relationship with the impeller to improve brake cooling for vehicles having low speed duty cycles.
Brake drum temperatures can become excessive for vehicles with low speed duty cycles, such as garbage trucks and buses, for example. These types of vehicles have duty cycles that typically include a significant amount of stops and starts over a short period of time. Further, these vehicles usually do not operate at uninterrupted higher speeds for any significant amount of time. Thus, the brake drum and other associated brake components can become overheated. Excessive and extreme temperatures can reduce brake component life and can adversely affect vehicle performance.
Brake cooling mechanisms such as fins and drum turbines have been incorporated into brake drums to provide increased cooling for the brake components. For example, a drum turbine uses a separate stamped piece that is mounted to the external surface of the drum. The stamped piece includes a plurality of vanes formed about the circumference of the brake drum that help direct heated air away from the drum. The vanes are formed to direct air radially outward from the external surface of the drum. However, these brake cooling mechanisms may not perform adequately in low speed applications. In some low speed applications, these brake fins or drum turbines can actually increase the temperature of the brake drum, which is undesirable.
For the above reasons, it would be desirable to provide a method and apparatus for improving brake cooling during low speed, high stop and start applications, in addition to overcoming other deficiencies in the prior art as outlined above.
The invention is directed toward a method and apparatus for cooling a brake assembly. The brake assembly includes a brake drum with an impeller mounted for rotation with the brake drum about an axis of rotation. A non-rotating stator is held fixed relative to the drum. Cooling external air is drawn in an inboard direction across an external surface of the brake drum via the impeller and the heated air is directed away from the brake drum in an inboard direction generally parallel to the axis of rotation by the stator.
In the preferred embodiment, the brake assembly includes the brake drum that has an inner cavity defining a braking surface. The impeller is mounted for rotation with the brake drum and has a plurality of impeller vanes formed about the circumference of the impeller. The stator is preferably mounted to an axle and does not rotate with the brake drum. The stator includes a first portion for directing airflow across an external surface of the brake drum and a second portion having a plurality of stator vanes that direct the airflow away from the brake drum in a direction generally parallel to the axis of rotation.
The first portion is preferably a circular band that is positioned in an overlapping relationship to the impeller. The second portion, which is integrally formed with the first portion as a single piece, is formed transversely with respect to the first portion and extends radially inwardly toward the axis of rotation to define a vertical face. The stator vanes are formed within the vertical face. Preferably, each stator vane includes at least one tab member that extends outwardly from the vertical face. Each stator vane is positioned at a unique radial position on the vertical face relative to the axis of rotation.
The subject invention provides an impeller and stator combination that draws external cooling air across the brake drum and toward an inboard direction of the vehicle to maximize the cooling effect. These and other features of the present invention can be best understood from the following specifications and drawings, the following of which is a brief description.